488 On the Construction of Kitchen Fire-places^ etc. 



becomes cold, the steam-tubes will be entirely filled 

 with air. 



When, on lighting the fire again, fresh steam is gen- 

 erated, as this steam enters the large steam-tubes in 

 the highest or most elevated part of them, and as steam 

 is specifically lighter than atmospheric air, the steam 

 remains above the air which still occupies the steam- 

 tubes, and accumulating there presses this air down- 

 wards, and by degrees forces it out of the apparatus 

 through the same passage by which it entered ; the 

 water in the semi-circular tube supplying the place of 

 a valve, or rather of two valves, in these different 

 operations. 



[This paper is printed from the English edition of Rumford's Essays. 

 Vol. III., pp. 1-384.] 



